can I stream a movie from my macbook or iPad and watch on my tv with the apple tv?

Yes, if it's in iTunes (MB) or stored (iPad) you use airplay.

If it's through an app on iPad it would need to be enabled for airplay.

You could also use mirroring but the device would need to be compatible.

http://support.apple.com/kb/HT4437?viewlocale=en_US&locale=en_US

http://support.apple.com/kb/HT5922

http://support.apple.com/kb/ht5209

http://support.apple.com/kb/ht5404

I use the "Beamer" application on my iMac to stream video to my ATV3. It works like a champ. The benefit of this application over mirroring is that it allows you to use the Mac for other tasks while streaming your video content.